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Your mixture needs adjustment. Your running to rich. You get hunting because a warm engine runs with the idle motor almost closed and it has very little power to move the idle motor at closed locations. Try closing your curb idle screw a little more (turn CCW a little) after your adjust your mixture.

Originally Posted by dmcnc

Like Dave said, your low numbers indicate rich setting (lean correction). I would adjust the curb idle by turning the curb idle screw up until the RPMs increase then back it off an 1/8 to 1/4 turn. You can use your RPM tachometer on your multimeter (this function is 6 cyl) hooked up to the coil wire to identify the spot where your RPMs increase.

If your dwell numbers stay the same afterwards, move on to CO adjustment, which will require you to VERY carefully drill out the CO adjustment plug. You will also need to make sure you have something to plug that hole after each adjustment and once the procedure is complete.

Thank you! I was worried that the numbers would be perfect and I'd still be on the hunt. This is promising, I'll carefully remove the plug and get to adjusting. Hopefully this solves the problem. I imagine that since car runs so well while the enrichment cycle is still going that there probably isn't something else going on... I hope

Thank you! I was worried that the numbers would be perfect and I'd still be on the hunt. This is promising, I'll carefully remove the plug and get to adjusting. Hopefully this solves the problem. I imagine that since car runs so well while the enrichment cycle is still going that there probably isn't something else going on... I hope

Ok so I corrected the fuel mixture, it took only about a quarter turn.
But I'm still getting some jerky acceleration usually right around 20000 RPMs. I remember that I had this issue before, and I replaced the spark plugs and it seemed to fix the issue, but now its back. Cold it be that the rich condition messed up the spark plugs? Could my coil be going bad, rotor cap, or wires? Looks like I'm still going to be tinkering about with this.

A 1/4 turn on one that hasn't been tampered with is a lot!
Does it do OK above 20,000?

It might not have been that much to be honest, I just mean that it didn't have to be turned much, may have been a 1/16 of a turn.
but yes, its way better at higher RPMs. The dwell reading now swings right around 40-50. I guess the next step is to check fuel pressure?

It might not have been that much to be honest, I just mean that it didn't have to be turned much, may have been a 1/16 of a turn.
but yes, its way better at higher RPMs. The dwell reading now swings right around 40-50. I guess the next step is to check fuel pressure?

If you didn't answer that it was OK above 20K, I would have suspected that adjusting the CO compensated for a problem in the fuel system and went from there...

I would expect new plugs to clean up after driving around a bit. But at this point, I would double check the plugs (or install a set of AC Delco, if different than those installed when it ran OK before), vacuum leaks (use smoke), and all base settings (timing, at idle and at 20K; primary AND control pressures; etc). Then set the dwell where it swings 35-45, checking it with everything in place (including the breather and factory plug) and given a few seconds for things to settle after changing it.

A 1/16 turn is still a lot... To get an idea of how touchy it is- to change the dwell from the 40-50 you have to the 35-45 spec, expect to turn it as little as you can several times before you get it right.

If you get down to checking the coil, make sure you include shaking it. If you hear or feel the oil in it, toss it.

If you didn't answer that it was OK above 20K, I would have suspected that adjusting the CO compensated for a problem in the fuel system and went from there...

I would expect new plugs to clean up after driving around a bit. But at this point, I would double check the plugs (or install a set of AC Delco, if different than those installed when it ran OK before), vacuum leaks (use smoke), and all base settings (timing, at idle and at 20K; primary AND control pressures; etc). Then set the dwell where it swings 35-45, checking it with everything in place (including the breather and factory plug) and given a few seconds for things to settle after changing it.

A 1/16 turn is still a lot... To get an idea of how touchy it is- to change the dwell from the 40-50 you have to the 35-45 spec, expect to turn it as little as you can several times before you get it right.

If you get down to checking the coil, make sure you include shaking it. If you hear or feel the oil in it, toss it.

So I was planning to install my new DMC fuel pump sender combo today but I had over half a tank. So I decided to just drive it all out. I took along my meter and an the 3mm allen wrench. After I drove for a while I hooked up the dwell and it was back to being rich, like I had never adjusted it. "what the heck! what is going on" so I adjusted it back to fluctuating around 45, and the jerky acceleration seemed to go away. "is it fixed? why did it revert back to being rich?"

Anyway, after that I drove around even more until the gas was low, and my old fuel pump started to get loud like it does when it gets hot.
Went back and started the process of installing the new pump. I uninstalled the old pump and the baffle. The boot had a nasty molasses like substance under it around the connections, and the pick up hose was all worm, soft and sticky. So I syphoned out the remaining gas, and dried the tank, and shop vaced it out. I made it like brand new in there, you could eat off of the inside of that tank now. I finished the installation, filled the tank, and took to the streets. Seems to be running good now. Dwell reading are correct, and wasn't getting any jerky acceleration. Idle is steady right form start up. the only thing I can say now is that there my be a bit of vibration at idle. This may be normal? I Only notice it when the AC is on. maybe the extra load I guess. Anyway I will continue to test and all that.
Next week I'm going to be replacing the lines to my FV with SSlines, and the send and return lines, which will complete the conversion to all SSlines in my engine compartment, no more plastic lines.
If anyone has any ideas about why the mixture adjustment seemed to have reset it self, let me know.

Dumb question, but are you plugging the CO adjustment screw hole after you make the adjustments and go for a drive?

I am,
I only remove the plug long enough to make the adjustment then replace it to check the result.
It's not a dumb question, if someone where doing that it would be important to know in order to help them Assuming they already know could cause something like that to be overlooked. So from here on out there are no dumb questions Assume I know nothing, and I promise not to be insulated. lol

After I drove for a while I hooked up the dwell and it was back to being rich, like I had never adjusted it. "what the heck! what is going on" so I adjusted it back to fluctuating around 45, and the jerky acceleration seemed to go away. "is it fixed? why did it revert back to being rich?"

Intermittent vacuum leak?

We pulled hair on one where the dwell would randomly change after a day, weeks, no telling...
Long story short- The roller that the FD's plunger rides on had seized up from sitting for years. Later, a flat spot wore on the roller. Then it freed up (some)...

We pulled hair on one where the dwell would randomly change after a day, weeks, no telling...
Long story short- The roller that the FD's plunger rides on had seized up from sitting for years. Later, a flat spot wore on the roller. Then it freed up (some)...

Curious as to why you keep setting the dwell to 45° instead of 40°?

because I'm ad idiot and thought thats what it was supposed to be set at. LOL
I'm sure I'm no done adjusting it. I'm going to change those remaining lines in the engine compartment this week, and then I'll make a new adjustment. I can't find a leak, at least not with carb cleaner.
When I change the lines to the FV is there a way to clean the FV while I have it out? Is this a good idea?
Thanks